Anthropic Principle

A
controversial cosmological principle that the observable universe, as it is,
must be compatible with our powers of observation, or else we would not be able
to observe it. Exponents of the
principle will often point out that the universe appears to be fine tuned,or
delicately balanced in its basic physical processes, to allow for the existence
of carbon-based life. Although
there are many versions of the principle, usually one can distinguish between
(a) the Weak Anthropic Principle, which affirms simply that the existence of
human life itself implies that nature must be consistent with having evolved
carbon-based life, and (b) the Strong Anthropic Principle, which is concerned
with the possibility of alternative universes, yet goes on to state
metaphysically that our observable universe must be the only kind of universe
capable of evolving human-like creatures as observers.

Only a small range of possible values for the universal constants (such as
the mass of an electron) are consistent with the presence of life as we know it.
The significance of such apparent fine-tuning of the universal constants is
disputed by those who regard it as trivial and those who argue from it to the
necessity of life in the universe.